Water quality is an issue of major concern in the
Mississippi River watershed where nitrate loading is known to result in
phytoplankton blooms that cause severe hypoxic conditions in the Gulf of
Mexico. In addition to the hypoxia problems, many midwest ern municipalities
derive their drinking water from reservoirs that frequently exceed the maximum
contaminant level (MCL) for nitrate. The majority of NPS derived pollutants
entering midwestern streams can be attributed to agricultural practices (USEPA,
1 992). In 1986 it was estimated that 50 to 70% of the assessed U.S. surface
waters were adversely affected by agricultural NPS pollution (USEPA 1986). In
addition, state NPS assessment reports identified agriculture as the greatest
NPS pollution problem in the U.S. (CAST, 1992). Illinois water quality data reflected
this same trend. Of the surface waters surveyed, 54% of the streams and 88% of
the lake acreage did not meet full use support criteria with 41%and 91% of all
use impairments in streams and lake s, respectively, derived from agriculture
(IEPA, 1992). In a recent study on the Embarras River, Champaign County,
Illinois (David et al. 1997), 96% of the annual nitrate load was derived from
agriculture. Similar results were found in an Iowa study (Keen ey and Deluca,
1993).

resulted in a 1992 IEPA directive to the city of
Bloomington, Illinois (authorized by the USEPA) to reduce its maximum drinking
water nitrate contaminant levels to below 10 ppm. Although some progress has
been made, the city will not meet the directive 's dead line of June 1997. A major
issueis the cost of engineered
systems designed to remove nitrates from drinking water. At the present ion
exchange, the most cost effective treatment available to remove nitrate, is
still quite expensive. Estimated cost ofinitial construction for a 20 mgd plant is $ 8million with $
1million for yearly maintenance and brine disposal. In addition, the
construction of treatment facilities is not in keeping with the recen t EPA
goal of "source water protection" (a watershed approach). Presently,
Bloomington and other Illinois municipalities (Danville, Decatur and Peoria)
seek less expensive more ecologically sound watershed based approaches to
remove nitrate from water sup ply reservoirs. These including the potential use
of wetlands as a method to remove agricultural pollutants before they enter
drinking water reservoirs and fertilizer input management.

Excessive concentrations of nutrients in streams draining
agricultural areas can be attributed to agricultural systems that
characteristically "leak" nutrients (Loucks, 1979) because N
fertilizer is ineffectively taken up by monoculture cropping (Keene y, 1982;
Simonis, 1988). These leaky systems are further exacerbated in the Midwest by
extensive tile drainage. On 37% of these agricultural lands, tile drainage has
decoupled wetland systems from the wetland/riverine interface, shunting
contaminated upla nd drainage water directly to main river channels (Fausey et
al., 1995).

In a recent study on the Embarras River at Camargo,
Illinois, we have shown that drainage files are the major source of nitrate
entering the river causing concentrations to repeatedly exceed EPA suggested
MCLs for nitrate (David et al., 1997). Improvem ents in surface water quality
will require the implementation of strategies and management practices that
reverse these effects by directly reducing nitrate application through
fertilizer management and, by reducing nitrate output from tile drainage syste
ms to streams using techniques such as constructed wetlands. Constricted
wetlands may prove to be a practical, economical, and effective method to
reduce surface water nitrate contamination. These "wetlands" are
formed by berming an area adjacent to a str eam and forming a small detention
basin or holding pond that intercepts file drainage water before it enters the
stream. The basin acts to reduce transport of nitrate in drainage water through
plant uptake and microbial transformation and degradation. Fol lowing

wetland treatment", drainage water is slowly
released to the stream, through regulated flow. Research on constructed
wetlands addresses the IWRC interest areas of watershed protection, water
quality and supply for small communities, and wetlands proces ses and
management; and may provide new methodologies to resolve associated water contaminant
problems.

STATEMENT OF RESULTS OR BENEFITS:

Constructed wetlands dearly have the potential to improve
and sustain water quality throughout the Midwestern agricultural region. We
propose an inexpensive and sustainable method to reduce nitrate input to Lake
Bloomington. Through the use of input/ou tput budgets, our research will
document the effectiveness of constructed wetlands in removing nitrate from
agricultural tile drainage waters, before entering Lake Bloomington. We will
also determine the rate of subsurface leakage and its effect on N remo val
efficiencies of the constructed wetlands. This work will be conducted
seasonally over at least two growing seasons. A multi-seasonal approach is
important because tile drainage inputs to the wetlands is weather dependent and
is expected to vary greatl y from year to year. In previous work we have found
that large flows over a few days can provide most of the year's input of
nitrate. Wetland function (denitrification) is thought to be highly temperature
dependent, so that the timing of these inputs may be critical to nitrate
removal. We do not know at this time how the wetlands will function at various
times of the year. Without this understanding, it is not possible to generalize
about their effectiveness.

Once we obtain several years of detailed information from
the Bloomington constructed wetlands, we will be able to make recommendations
to the municipality, landowners and farmers. The results of this work may
potentially have a large and sustained imp act on farming systems throughout
the Midwest We expect to be able to recommend an inexpensive, yet functional
wetland ecosystem that can be added to many, if not most, farming systems that
include tile drainage. Our recommendations would include the size of wetlands
needed per acre of tile drainage. This system could be demonstrated and
recommended to towns and cities in Illinois that depend on surface water
supplies for drinking water. Constructed wetlands could provide sustained
treatment of tile drain age waters, cleanup surface waters, and provide the
many benefits of wetlands that are currently absent in most Midwestern
agricultural ecosystems.